This invention relates to a pivotal mechanism for use in optical systems. More particularly, the invention relates to an improved pivotal or flexural mechanism that is inexpensive, stiff in directions other than the direction of rotation, and insensitive to temperature variations. Even more particularly, the invention relates to a flexural mechanism that can be designed to selectively place the pivot axis at a desired location, such as at the center of gravity of the mass being rotated, even when that desired location is outside of the mechanism.
Mirrors are used in optical systems to direct a beam of light to a desired location. In most optical systems it is necessary to be able to rotate the mirror in order to change the location of the directed beam. The amount of rotation is usually small, typically only a few degrees in either direction, but this rotation must be precisely controlled.
A variety of pivotal mechanisms upon which mirrors and the like may be mounted are known in the art for providing the needed rotational capability. However, all such mechanisms known to applicants have one or more disadvantages associated with the use thereof. These disadvantages include limited life, high cost, high temperature sensitivity, lack of needed mechanical strength in directions other than the direction of rotation, bulkiness, a fixed pivot axis, and excessive noise. (For purposes of pivotal mechanism terminology, and for purposes of this application, noise is defined as a jerkiness in the rotation of the mirror, typically caused by differing amounts of friction in the mechanism as it causes the mirror to rotate.)
Some examples of pivotal mechanisms known in the art include: (1) a shaft mounted in ball bearing; (2) elastomeric hinges; (3) a shaft mounted on jeweled pivots; and (4) "Free Flex" pivots, manufactured by the Bendix Corporation. ("Free Flex" is a registered trademark of the Bendix Corporation.)
Disadvantageously, shafts mounted in ball bearings have a limited life, exhibit excessive noise, and have a fixed pivot axis at the centerline of the shaft. While a shaft mounted on jeweled pivots reduces noise, such mechanisms still exhibit some undesirable friction and suffer from a limited life and a fixed pivot axis. Elastomeric hinges are bulky, temperature sensitive, noisy, and mechanically weak in directions other than the direction of rotation. Further, it is difficult to precisely define the pivot axis of an elastomeric hinge.
There is, therefore, a need in the art for an improved mechanism that does not suffer from the above disadvantages.